The proposed R21/R33 application "Micro Lock-In Amplifier for Cortisol and Catecholamines" will explore the design hypothesis that a new microimmunoassay device can rapidly detect multiple analytes in saliva to better understand the effect of stress on health. Stress in general and cortisol, specifically, has links to cardiovascular health, bone density, diabetes, obesity, autoimmune disease, reproductive health, and cognition. The proposed new system would bring advances in miniaturization and magnetorheology together to improve the detection limit in competitive immunoassays through a lock-in amplifier signal conditioning system. Multi-channel competitive immunoassays for rapid quantitation of analytes in saliva are sought as a means to simultaneously visualize time-dependent changes in biomarkers of stress, such as cortisol, as a risk for disease. Saliva sample collection is desired over blood and other bodily fluids for many reasons. In our proposed research, the most important purpose for using saliva is the promise of drawing samples quickly in order to catch dynamic responses. Currently, cortisol and catecholamines are measured individually and usually from blood. In collection of blood for cortisol analysis care must be taken with cannula insertion, and there must be a 45 minute wait after cannula insertion to draw the first baseline sample. Thus, use of blood samples and cannula use, can limit situations in which cortisol measurements can be taken. It can also limit the populations that can be studied as well, since there is a reluctance to use the cannulas in children, and sometimes in older subjects as well. The outcome from this research is the expansion of the current suite of analytes measurable in saliva and the streamlining of sample collection and processing to "image" bodily responses to stress and other external stimuli. Applications to wellness, therapeutic drug monitoring, and bio or chemical exposure are envisioned using the general approach of microlock-in amplifier detection technology.